Vintage Dirt Bike Q & A

I just finished a restoration on a 78 250R (stock) and am considering some vintage mx racing. Is there anything unique to this model mechcanical or otherwise to do or watch out for that could be an advantage/diadvantage/problem? I will be in the novice division.
thanks

You can definitely race this bike as is. However, I would highly recommend a set of Fox Shox or Works Performance shocks, and modifying your stock forks to reduce the compression damping (I can send you the Al Baker "mod" instructions). After that there are plenty of other things you can do. See pictures...

http://www.thumpertalk.com/forum/garage.php?do=viewvehicle&vid=6156

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

Thanks redrocket for the info and pics. My email address is mailto:mesbrown@comcast.net I don't think I've run across the Al Baker info yet. Any other reliability issues?

If you do not know the history of the motor and have any doubts in that department have the crank seals, crank bearings, bottom-end and top-end inspected. I learnt the hard way to spend a little money up-front for peace of mind. Also a Mikuni carb will clean up your jetting perfectly.

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

Hi,
If you have the stock (countershaft sprocket) chain guard, the one that has the rear attachment going to a case screw, I'd remove it. Chances are that if you ever throw a chain with this early piece of hardware attached, you're going to get some nasty case damage. The improved '79 and '80 chain guard models attached to a bracket just forward of the swingarm pivot. Also, if you buy a bike, or a spare motor on an auction, get a good closeup photo of the crankcase just in front and behind the countershaft where the csae screws are located.

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1978 CR250R
1979 CR250R
1980 CR250R
1980 ME360
1986 CR250R

Remove the counter shaft sprocket cover whichever model you have. It will get nuked if the chain ever comes off and they are very difficult to replace. Better yet see if you can fabricate a case saver...

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

This is the place! Listen to what those guys say, I did and it saved me a lot of grief. Redrocket is a guru! I went to the Suzuki forum(I think thats it) and got the info for making a leakdown tester and sure enough, both motors had blown base gaskets and one had leaking crank seal.
Now I have one complete bike that is awesome, got some 41mm front forks(ebay) had to wait a little longer finding a tree. I'll be doing a complete on the other motor this winter, hot rod crank, bearings, seals and I'll be ready for AHRMA this spring!
I think its pretty cool the guys on this sight help other guys out.
Now if I could just find a front sprocket chain guard.
Oh, by the way, base gaskets go in dry, seems the cr250 is notorious for blowing base gaskets, my 2 cents.

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Garry Mainer
#33m (retired)
Honda Cr250r 1980
Honda Cr250r 1980
Yamaha TY250C 1976
Arctic Cat 650 H1 2007

http://www.thumpertalk.com/forum/garage.php?do=viewvehicle&vid=6156 This is what you could get into. Luckily I received therapy before I got into the Mugen kits, Fox forks etc. etc...

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

Yeah, as far as the sprocket covers for the 78-80 units, I have a box of brand new take-offs. I never used 'em.
As I think a little more about maintenance on these bikes, be sure to grease the swingarm pivot bearings on a regular basis. Water has a way of easily getting in there. Also, keep the kickstart lever pivot well lubed. If you don't, the aluminum lever will wear quickly and I have seen some that have been neglected so long that they flop around and damage the side of the clutch cover. I have been buying used kickers, enlarging the wallowed pivot hole and machining a larger pin to fit with a zerk fitting at the top. The inside of the pin has a small hole drilled almost full length with another two perpindicular holes intersecting at the bearing contact area of the lever for grease flow to points of contact.
Another area that is prone to quick wear is the rear brake actuator lever where the brake rod goes through the aluminum pin. The aluminum pin wearing the hole of the aluminum lever is not good. I have replaced the aluminum pins with strainless ones that I have made. This does prolong the life of the lever and the pin. The lever is getting harder to find.

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1978 CR250R
1979 CR250R
1980 CR250R
1980 ME360
1986 CR250R

thanks for the replys ... good stuff. I had the motor totally rebuilt and did not put the chain gaurd back on. (It didn't look like it would do much to stop a thrown chain!!) What do you guys do for the wear items such as the chain gaurd on the swing arm and the chain rollers?? Try to find stock replacments??? fab something up???

Fortunately, I still have a small invenrory of rubber chain buffers. I believe there's an aftermarket chain buffer on eBay right now. The seller/maker is in Australia. The item is a stiff $55 +shipping, however.
Item number: 250053166769
As far as the rollers go, none of the 78-80 rollers were (in my opinion) any good. The '79 had an aluminum roller with a caged needle bearing setup. The needle bearings are a little too light duty for the application and quickly become toast. You can find after market sealed ball bearing units that will do the job. There's a stock '79 roller on eBay right now if that's the way you want to go, Item number: 220052068007 .

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1978 CR250R
1979 CR250R
1980 CR250R
1980 ME360
1986 CR250R

Hi GoForDucks

Can you give me the plan for the leakdown tester please.

It would be most appreciated.

many thanks

Ruairi- England

Heres the link, its on the Suzuki forum under Leak down tester also.
I made one and found base gasket leak right off the bat!!
Its kinda hoakie, but it works providing you get the exhaust to seal off good, I used part of an old innetube with a hose clamp. The intake part was easy, hardware store for the pvc and tire shop for the air valve.

http://alp-sys.com/vintagedirtbikeforum ... eak+tester

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Garry Mainer
#33m (retired)
Honda Cr250r 1980
Honda Cr250r 1980
Yamaha TY250C 1976
Arctic Cat 650 H1 2007

Hey Redrocket, that link you have for your bike and rebuild cost is awesome!! Saved it to file for future reference...Thanks for sharing!!

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Garry Mainer
#33m (retired)
Honda Cr250r 1980
Honda Cr250r 1980
Yamaha TY250C 1976
Arctic Cat 650 H1 2007

KTM, here's an option for the rubber chain guard that goes on the swingarm, it will get you going.
I went to a repair shop for diesel engines and got a used radiator hose, the biggest you can find, cut it in half length ways, laid it flat on the work bench, traced the old guard on and cut it out drilled the holes and used a moto tool to grind out the back side for clearance where the welds are at on the swing arm and put it on, the one I made has about 6 hours on it now and still looks pretty good. Nice thing is you can usually get the hoses for free if you know a mechanic that will save them for you.

_________________
Garry Mainer
#33m (retired)
Honda Cr250r 1980
Honda Cr250r 1980
Yamaha TY250C 1976
Arctic Cat 650 H1 2007